Emotional instability as an indicator of strictly timed infantile developmental transitions

There are indications that periods of disorganization/instability/regression accompany developmental transitions in early infancy. The goal of the present study was to validate a pattern of 10 strictly timed periods of emotional instability found through maternal reports by van de Rijt-Plooij & Plooij (1992a), by means of ethological observations. A longitudinal study was carried out on four mot her-infant pairs which were followed up weekly during a period of 15 months. The results failed to support the 10-period pattern. Possible explanations for these findings are presented, together with a discussion about methodological aspects of the data analysis.